In this Phase II program we propose continued development of a new nitric oxide (NO) sensor. The sensor is intended for use in assessment of airway inflammation with applications in asthma diagnosis and management as well as in other health care applications involving inflammation in the gastrointestinal tract and the urogenital organs. We use the relatively new Quantum Cascade (QC) distributed feedback semiconductor lasers and flexible hollow waveguides that serve as a light guide and a gas sample cell to produce a tunable Mid-InfraRed semiconductor Laser Absorption Spectrometer (MIRLAS). The QC lasers operate in the mid-infrared region of the electromagnetic spectrum where NO exhibits a strong band of absorption. We use wavelength modulation spectroscopy to provide measurements that are species specific to assure that measurements are relatively free of interference effects from other constituents of the sample stream. The small sample volumes presented by the hollow waveguide and a proprietary gas exchange assembly provide for rapid response to gas concentration changes. In Phase I, using MIRLAS, we demonstrated a 58.8 ppb NO detection limit with a 0 to 90% rise time of 0.48 s. These measurements are the first of their kind reported in the world. The feasibility of our approach has been clearly demonstrated. The markets for such a device are extensive. The instrument is compact and lightweight and could easily be deployed in physician's offices, health care clinics and emergency rooms. As an indicator of the commercial significance Arete Associates has formed a strategic alliance with Aerocrine AB, a commercial medical device company specializing in airway inflammation diagnosis. Plans for development and marketing are ongoing and evidenced by their participation in this program. [unreadable] [unreadable]